The present invention relates to the field of digital computer systems, and more specifically, to a method for identifying potentially fraudulent usage of a user identifier of an information or communication service.
Nowadays, most of instant messaging applications use the phone number as the primary key to uniquely identify a contact. Sometimes it happens that users change their phone number and their original phone card is not reset, but reassigned to a different account. Current instant messaging applications are not able to properly handle this scenario and report the old account as still associated to the original contact. Users already having that contact in their phone address book have no evidence of the above condition. This may lead those users to share personal information to unauthorized people. In addition, users could provide fake identities to other users.